Run-flat tire

Abstract

A run-flat tire capable of reducing weight and enhancing its uniformity. The run-flat tire 1 provides a toroidal carcass 6 extending from a tread portion 2 to the bead core of each bead portion 4 through each of sidewall portions 3 and a pair of side reinforcing rubbers 9 arranged inside the carcass 6 and extending along the sidewall portions 3 in the tire radial direction inwardly and outwardly. In the outer surface of the tread portion 2 , pattern elements are arranged, thereby forming a pitch pattern. Each of the side reinforcing rubber 9 provides with recesses 11 circumferentially spaced on the inner surface of side reinforcing rubber facing the tire cavity. The total number (n) of recesses 11 on each of the side reinforcing rubber 9 is 0.70 to 1.30 times the total number of pattern elements.

1. A run-flat tire comprising a toroidal carcass extending from a tread portion to a bead core of each bead portion through each of sidewall portions, and a pair of side reinforcing rubbers arranged inside said carcass and extending in the tire radial direction inwardly and outwardly along the sidewall portions; wherein
 on the outer surface of said tread portion, a pitch pattern is made of pattern elements, which is the minimum unit of repeat pattern, aligned in the circumferential direction of the tire; 
 each of said side reinforcing rubbers is provided with recesses circumferentially spaced on the inner surface of the side reinforcing rubber facing the tire cavity; and 
 the total number (n) of recesses on each of the side reinforcing rubbers is 0.70 to 1.30 times the total number of pattern elements, wherein 
 a phase difference δ between a primary component of the pitch pattern and a primary component of a recess array pattern is not more than π/2 (rad), 
 the primary component of the pitch pattern is obtained by substituting an unit pulse for each of the pattern elements of said pitch pattern, in which a pulse row is formed in an array sequence of the pattern elements with reference to a single pattern element, and in which the pulses are spaced from each other in the circumferential direction by a pitch of circumferential length of the pattern elements, and by expanding the pulse array to a Fourier series; and 
 the primary component of the recess array pattern is obtained by substituting an unit pulse for each of the recesses of said recess array, in which a pulse row is formed in an array sequence of the array of the recess with reference to one of recesses of the corresponding positions to said reference point of the pattern element, and in which the pulses are spaced each other in the circumferential direction by a circumferential length of the recess, and by expanding the pulse array to a Fourier series. 
 
     
     
       2. The run-flat tire as set forth in  claim 1 , wherein said recesses are substantially in the same configuration, disposed in the same position of the tire in the radial direction, and spaced by a constant pitch in the circumferential direction of the tire. 
     
     
       3. The run-flat tire as set forth in  claim 1 , wherein said recess comprises at least three kinds of pitches each of that is a length in the circumferential direction of the tire, and the pitches are arranged in a random manner. 
     
     
       4. The run-flat tire as set forth in  claim 1 , wherein
 said recess comprises at least three kinds of pitches each of that is a length in the circumferential direction of the tire, and the pitches are arranged in accordance with a chaotic function. 
 
     
     
       5. The run-flat tire as set forth in  claim 1 , wherein
 in a profile of the tire outer surface on the tire meridian section including the axis of the tire under a standard unloaded state, which is mounted on a standard wheel rim, at standard inflation, and unloaded,
 if a point is identified as the point (P) on an outer surface of the tire separated by a distance of 45% of the tire maximum width (SW) from an intersection point (CP) of the tire outer surface with the tire equator (C), the curvature radius (RC) of the tire outer surface reduces gradually outwardly toward the axial direction in an interval between the above-mentioned intersection point (CP) and the above-mentioned point (P); and 
 
 the relationships are formulated as follows:
   0.05< Y 60 /H≦ 0.1 
   0.1< Y 75 /H≦ 0.2 
   0.2< Y 90 /H≦ 0.4 
   0.4< Y 100 /H≦ 0.7 
 
 wherein each (each of Y 60 , Y 75 , Y 90 , and Y 100  is the distance between the said intersection point (CP) and each of points P 60 , P 75 , P 90 , and P 100  on the tire outer surface separated in the tire axial direction by a distance of 60%, 75%, 90%, and 100% of half the tire maximum axial width (SW/2) from said intersection point (CP); and 
 the above-mentioned “H” is a cross-sectional height of the tire.